What are cookiecutter sharks? Boat attacked by glow-in-the-dark predators

What attacks nuclear submarines, glows in the dark and looks like “a pencil with teeth”?

Give up? It’s a type of shark called a cookiecutter shark, so named because its vampirish teeth can take 2-inch round chunks out of much larger prey.

The sharks attracted worldwide attention this week for swamping a (no-longer) inflatable catamaran attempting a round-the-world voyage.

That voyage was cut short when a school of cookiecutters mistook the vessel for a whale — which is on their menu, along with dolphins, bluefin tuna and other, bigger sharks like great whites.

“They’re a really cool species of shark. This unfortunate incident has given us an opportunity to learn about them,” Prof. Jodie Rummer, a marine biologist at James Cook University in Australia, told The Guardian.

“They’re called the cookiecutter shark because they don’t actually swallow their prey,” Rummer added. “They just take little bite-size morsels out of the side of them.”

It gets weirder, Rummer said: “They’re bioluminescent too, they glow.”

Cookiecutter sharks (Isistius brasiliensis) grow as large as 18 to 20 inches long. Because they’re small and live in the deep water column, they don’t receive much attention or academic study.

The sharks usually feed in the deep ocean during the day and near the surface at night, so they spend much of their lives in darkness.

A parasitic species, cookiecutter sharks have an “odd and somewhat frightening array of teeth they use to grab their prey and twist to bite a circular piece off,” Daryl McPhee, associate professor of environmental science at Bond University, told ABC.

They “really just look like a pencil with teeth,” McPhee added.

And they’re not picky eaters: Cookiecutters have been known to chomp down on undersea cables and the sonar components of nuclear submarines.

The ReefQuest Centre for Shark Research relates how “[d]uring the 1970’s, several American subs were forced to return to base due to cookiecutter damage to their neoprene-covered sonar domes, which caused the sound-transmitting oil to leak out and rendered the enormous subs effectively ‘blind.’

“[T]he US Navy must have had nightmare visions of a completely unknown, rather diabolical, enemy weapon.”

But are they maneaters? Again, they’re not picky, and they’ve been known to try a bit of human flesh here and there before moving on.

A cookiecutter shark attack was reported in Hawaii in 2011, when the victim was swimming in deep water at night. Another attack occurred in 2017 off Magnetic Island in Australia. Both victims survived.

But a real attack would be extremely painful, because the sharks travel — and dine — in schools.

“If you can imagine, they’ve got limited vision and it’s dark. They see an inflatable catamaran with a big surface area that is soft and flat. ‘Is it a whale? Let’s have a look. Oh, yep, that tastes like rubber. It’s not for me,’” said Rummer.

That’s probably how a few small sharks were able to swamp a 30-foot inflatable catamaran. “[T]his species does often travel in schools and if they’re all going at this inflatable thinking it’s a potential food item, that’s where you damage as there are multiple bites,” she added.